Anaxagoras’ theory of matter offers a problem which, in bald outline, may be stated as follows. The theory rests on two propositions which seem flatly to contradict one another. One is the principle of Homoeomereity: A natural substance such as a piece of gold, consists solely of parts which are like the whole and like one another—every one of them gold and nothing else. The other is: ‘There is a portion of everything in everything’, understood to mean that a piece (...) of gold , so far from containing nothing but gold, contains portions of every other substance in the world. Unless Anaxagoras was extremely muddleheaded, he cannot have propounded a theory which simply consists of this contradiction. One or the other proposition must be reinterpreted so as to bring them into harmony. Some critics attack one, some the other; some try to modify both. Mr. C. Bailey has recently published a fresh attempt to reconstruct the theory in a form consistent with itself. But the result, as he admits, is arbitrary and uneconomical. These defects, like all the contradictions and obscurities found in other accounts of the system, can be traced to the second proposition: ‘There is a portion of everything in everything’, or rather to the construction put upon it. The language is crude, vague, and ambiguous. What does ‘everything’ mean? Has the first ‘everything’ the same sense as the second ? If taken to mean that there is a portion of every material substance in every material substance, the proposition leads to a result for which ‘uneconomical’ is an indulgent epithet. (shrink)